Changes in the vibrational characteristics arising from the hydrogen bonding between N 2 and HNO 3. Ab initio and DFT studies

Abstract

The changes in the vibrational characteristics (vibrational frequencies, infrared intensities and Raman activities) arising from the hydrogen bonding between N 2 and HONO 2 have been predicted employing ab initio calculations at SCF and MP2 levels and DFT calculations. The predicted values with MP2 and DFT calculations are in better agreement with the experimentally measured solvent shifts than the predicted values with the SCF calculations. The most sensitive to the complexation is the stretching O–H vibration. The predicted frequency shift of the ν(O–H) with the MP2/6-31+G(d,p) is in the best agreement with the experimentally observed (−34 cm −1). The IR intensity of this vibration increases upon hydrogen bonding, up to 5 times and Raman activity increases up to 2 times. The magnitude of the solvent shift is indicative of relatively weak OH⋯N hydrogen-bonded interaction.